Third generation (3G) telecommunications systems based on Wideband Code Division Multiple Access (WCDMA) radio access technologies have just recently been deployed all around the world. Since user and operator requirements and expectations continue to evolve, the Third Generation Partnership Project (3GPP) has begun working on future telecommunications systems, so-called Long-Term Evolution (LTE) systems.
LTE systems will have an Internet Protocol (IP)-based network architecture that is currently standardized in connection with the System Architecture Evolution (SAE) project. The current status of the SAE network architecture is schematically illustrated in FIG. 1. Briefly, the SAE project specifies a split-type architecture with a user plane and a control plane. The user plane comprises user equipment (UE) 12, an Evolved Universal Mobile Telecommunications System Terrestrial Radio Access Network (EUTRAN) 14, one or more GW nodes 16, 18 and a Packet Data Network (PDN) 20. The EUTRAN 14 includes at least one RBS node not shown in FIG. 1. On the control plane, a Mobility Management Entity (MME) 22 is in charge of handling control plane signalling as well as mobility-related tasks. The MME 22 node interfaces a Home Subscriber Server (HSS) 24 which, among other things, stores subscription-related information.
Compared to 3G systems, the SAE network architecture is flat in that it comprises fewer types of network nodes. For example, the functions of Node Bs, Radio Network Controllers (RNCs) and Serving GPRS Support Nodes (SGSNs) of conventional 3G networks are now handled by RBS nodes, and GW nodes serve as common anchor points for all network access technologies.
According to the deployment variant illustrated in FIG. 1, the GW node is split into two dedicated physical nodes, a Serving GW node 16 on the one hand and a PDN GW node 18 on the other hand. According to a further deployment variant, the functionalities of the Serving GW node 16 and the PDN GW node 18 may be integrated in a single physical node.
The Serving GW node 16 interfaces the EUTRAN 14 and constitutes an anchor point for intra-3GPP mobility. The PDN GW node 18 interfaces the PDN 20 and serves as common anchor point for all network access technologies, providing a stable IP point-of-presence for all UE 12 regardless of mobility within or between access technologies. The MME 22 is kept separate from the GW nodes 16, 18 to facilitate network deployment and scaling of capacity. For this reason, only two node types, the RBS nodes and GW nodes 16, 18, need to scale in capacity to accommodate larger increases in network traffic.
Conventional mobile telecommunications systems according to, for example, the Global System for Mobile Communications (GSM) standard or the UMTS standard may be integrated into the LTE system. To this end, standardized interfaces are utilized between the LTE core network and a SGSN 26 that is coupled to an GSM EDGE RAN (GERAN) 28 and an UMTS Terrestrial RAN (UTRAN) 30 as shown in FIG. 1. The interface between the SGSN 26 and the MME 22 is utilized for transferring context information and establishing radio access bearers (RABs) when moving between different access types. The interface between the SGSN 26 and the Serving GW node 16, on the other hand, is utilized for establishing IP connectivity. The Serving GW node 16 basically acts as a Gateway GPRS Support Node (GGSN) for GSM and UMTS terminals.
A crucial advantage of the LTE network is its capability of providing Quality of Service (QoS) guarantees. To this end, each logical connection through the LTE network, also called tunnel, may be associated with a dedicated QoS class. Each tunnel has an associated Packed Data Protocol (PDP) context and RAB. Any user equipment may concurrently have multiple tunnels, possibly associated with different QoS classes.
It is expected that the introduction of mobile broadband services in connection with the deployment of LTE systems will lead to a drastic increase in network traffic. Current models predict that only approximately 10% of this network traffic will actually require a guaranteed QoS, while 90% of the network traffic will be Best Effort (BE) traffic not requiring any QoS guarantees. Obviously, it is desirable to take this traffic distribution into account when optimizing the LTE network architecture further.